U.S. patent number 4,406,285 [Application Number 06/227,709] was granted by the patent office on 1983-09-27 for manual radial and chordal keratotometry apparatus.
This patent grant is currently assigned to Richard A. Villasenor. Invention is credited to Leonard L. Krasnow, Richard A. Villasenor.
United States Patent |
4,406,285 |
Villasenor , et al. |
September 27, 1983 |
Manual radial and chordal keratotometry apparatus
Abstract
A cornea is altered in shape by providing a template body to
guide a surgical blade, the body being formed in a semi-spherical
hollow with the outer wall concentric with the inner surface of the
cornea and the inner wall of the template body concentric with the
outer surface of the cornea. The template body affords a rest
surface for a shoulder on the surgical blade to limit penetration
of the blade into the cornea in accordance with the thickness of
the template body, which varies inversely with the thickness of the
cornea to preclude blade penetration of the anterior chamber of the
eye behind the cornea. Guide slits in various patterns are formed
in the template body between the optic zone and the limbus circles
diameter of the eye to change the resistance of the cornea to inner
eye pressures and thus alter the corneal shape to correct focal
problems of the eye.
Inventors: |
Villasenor; Richard A. (Mission
Hills, CA), Krasnow; Leonard L. (Worchester, MA) |
Assignee: |
Villasenor; Richard A. (Mission
Hills, CA)
|
Family
ID: |
22854154 |
Appl.
No.: |
06/227,709 |
Filed: |
January 23, 1981 |
Current U.S.
Class: |
606/166; 33/1B;
33/21.1; 33/507; 33/512; 33/525; 606/107; 606/172; 623/5.13 |
Current CPC
Class: |
A61F
9/013 (20130101); A61F 9/0136 (20130101); A61F
9/0133 (20130101); A61B 2090/3937 (20160201) |
Current International
Class: |
A61F
9/007 (20060101); A61F 9/013 (20060101); A61B
19/00 (20060101); A61F 017/32 () |
Field of
Search: |
;128/1R,305,33R,305.1
;99/537 ;83/565 ;409/130
;33/1F,1SA,21R,21B,174D,174A,174B,174E,174G,1B ;604/116,117
;433/72,176 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
|
2300326 |
|
Sep 1976 |
|
FR |
|
725747 |
|
Apr 1980 |
|
SU |
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Other References
Schachar et al., Radial Keratotomy, "Proceedings of the Semi-Annual
Keratorefractive Society Meeting on the Controversial Aspects of
Radial Keratotomy," LAL Publishing, P.O. Box 1225, Denison, Texas
75020, 1980, pp. 201-212. .
"Shaping up the Blurry Eye" Toufeas et al., Time Magazine, New
York, Sep. 22, 1980..
|
Primary Examiner: Apley; Richard J.
Assistant Examiner: Kruter; J. L.
Attorney, Agent or Firm: Gribble; Wm. Jacquet
Claims
We claim:
1. Apparatus for guiding a surgical knife blade in keratotometry
refractive eye surgery comprising a template adapted to fit an eye,
a semi-spherical template body, fixation means on the template to
secure the template with respect to the eye, a central optic zone
on the template body, a visible locator index in the optic zone
visible from outside the template, said body having an obverse
surface concentric with the inner surface of the cornea and a
reverse surface concentric with the outer surface of the cornea,
and knife blade guide slits through the body.
2. Apparatus for guiding the path and controlling the penetration
of a surgical blade into the cornea of an eye during keratotometry
refractive eye surgery for the correction of myopia and astigmatism
and comprising a template, a template body, fixation means at the
periphery of the template, a central optic zone on the template
body, a visible locator index central of the optic zone, parallel
walls outside the optic zone defining guide slits in the template
area adjacent the optic zone and limited by the limbus circle of
the eye cornea being incised, said template body being
semi-spherical in shape with obverse and reverse curving surfaces,
the obverse surface being concentric with the endothelium contour
of the subject eye, and the reverse surface of the template body
being concentric with the epithelium contour of the subject eye to
control the penetration of the surgical blade, and knife blade
guide slits through the template body.
3. Apparatus in accordance with claim 2 wherein the guide slits are
defined by spaced, parallel walls extending radially from the optic
zone.
4. Apparatus in accordance with claim 2 wherein the guide slits are
defined by spaced, parallel wall pairs extending chordally in the
template area between the optic zone and the body periphery.
5. Apparatus in accordance with claim 2 wherein the guide slits are
defined by spaced pairs of parallel walls extending both radially
and chordally in the template area between the optic zone and the
body periphery.
6. Apparatus in accordance with claim 2 wherein said fixation means
comprises a suction cup secured to the template body, one cup at
each end of a body diameter.
Description
BACKGROUND OF THE INVENTION
While many attempts over the past years have been made to correct
surgically the vision defects detected by refractive examination
instead of corrective glasses or contact lenses, it is only since
the work of Dr. Sato of Japan was refined by Dr. Fydenoy of Russia
that numbers of researchers and doctors in the field have resorted
to surgical techniques with some degree of permanent success one
promising procedure is defined as "manual radial keratotometry"
wherein a plurality of deep radial cuts are made in the cornea of
an eye which refraction has shown to be myopic to allow internal
eyepressure to alter the corneal curvature to correct the visual
defect the cornea heals quickly compared to other types of tissue,
and the scar tissue from the surgery does not interfere with later
sight and is not obvious to an observer farther from the eye than
two feet while there is some danger of infection, as from any
surgical procedure, and differing periods for healing, freedom from
the need to wear corrective glasses or contact lenses is of greater
value to persons in certain professions, and has important
psychological advantages for other persons.
One problem with manual keratotometry in the past has been the
control of the depth of the incision, since too deep a cut may
damage the endothelium layer of the corneal inner surface and the
blade penetrates the Descemet membrane into the anterior chamber of
the eye. The endothelium is essential to the general health of the
eye and cell loss is permanent. On the other hand, if the incision
is shallow, the correction may not be permanent. Since the
thickness of the cornea increases from the central optic zone to
the circle of the limbus, the edge of the cornea, it is not
possible to merely carefully set the extension of the cutting point
from the guard or shoulder of the special scalpel to limit
penetration. While pachometry procedures can accurately guage the
thickness and profile curvature of the cornea there are few
practitioners capable of translating such parameters into manual
controls to effect radial or chordal incisions of sufficient
exactness as to accomplish the precise correction dictated by the
refractive, pachometric and keratometric measurements.
Therefore the method and apparatus of the invention are purposed to
overcome the possible imprecision of purely manual keratotometry
and to provide a method and apparatus aiding the surgeon to operate
simply and with precision, minimizing danger to the eye and to the
success of the procedure. The operation is one capable of being
performed in properly equipped doctor's offices and outpatient
clinics under topical anesthetic with anesthesia standby.
BRIEF DESCRIPTION OF THE INVENTION
The invention relates to manual keratotometry and more particularly
to manual keratotometry employing a mass-producible template for
guiding the surgical blade and the method for using the
apparatus.
The depth of the incision and the location on the cornea of the
incisions are critical. Therefore, the apparatus of the invention
comprises a preferably molded template body with semi-spherical
walls defining a shell of varying thickness from a central optic
zone to a periphery beyond the diameter of the limbus circle of the
eye. The central zone is marked with a visible indicator to aid in
placement of the template on the eye. Fixation means such as finger
grips or suction cups are at the periphery of the template body.
The curvature of the obverse or outer surface of the body is
concentric with the inner or endothelium contour of the cornea,
while the reverse or inner surface of the template body is
concentric with the outer contour of the cornea. Pairs of parallel
walls in the template body define guide slits for the surgical
blade in the zone between the optic zone circle and the limbus
circle diameters. The guide slits extend through the template body
and may be radial, chordal or both, in accordance with the vision
defect to be corrected. The template body may be molded of plastic
or stamped from metal, both of which materials are capable of
sterilization without harm to the device.
The process of the invention for keratotometric correction of
corneal curvature using a shouldered or guarded blade with
adjustable blade extension beyond the shoulder and employing a
blade template shaped in accordance with refractive and pachometric
data for the subject eye includes the steps of forming obverse and
reverse surfaces on a template body which are, respectively,
concentric with the inner and outer contours of the cornea. A
plurality of parallel pairs of walls are formed in the template
body to define guidance slits the depth of the body in accordance
with the corrective pattern for flattening the corneal curve
determined by the refractive and pachometric data derived from the
subject eye, and incisions are made in the cornea guided as to
pattern and depth by the template body contact with the shouldered
or guarded blade. The incisions are treated antiseptically and the
template removed from the eye.
The inventive apparatus and process afford simple precise means for
making more accurate a simple procedure without undue complication.
The data necessary for forming the templates is the same data
needed for the procedure. Templates may be made up from average
parameters in a range of dimensions and blade extensions adjusted
to compensate for subject cornea deviation from the average. The
apparatus may be molded economically from methyl acrylate or other
like plastic polymers. Alternatively the template may be of metal
which could be re-sterilized by autoclaving. In either material
cost would be nominal and accuracy assured.
These and other advantages of the invention are apparent from the
following detailed description and drawing.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a plan view of a template for radial keratotometry in
accordance with the invention;
FIG. 2 is a fragmentary plan view of the embodiment of FIG. 1 to a
greater scale;
FIG. 3 is a fragmentary sectional elevational view taken along line
3--3 of FIG. 2 showing the association between the device of the
invention and a subject cornea;
FIG. 4 is a schematic sectional view in operational orientation of
a subject eye and the embodiment of FIG. 1, both shown
fragmentarily;
FIGS. 5 through 8 are schematic plan views of templates in
accordance with the invention patterned for correction of different
vision defects;
FIG. 9 is a plan view to an enlarged scale of an alternate
embodiment of the invention having suction fixation appendages;
and
FIG. 10 is a fragmentary sectional elevational view taken along
line 10--10 of FIG. 9.
In the various Figures like reference characters are used to
designate like parts.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The embodiment of FIGS. 1-3 comprises a template 11 having a
template body 12 with a central optic zone 13 and a peripheral zone
14. The peripheral zone extends outwardly beyond a limbus circle 15
which defines the outer ends of a plurality of radial guide slits
16 extending from the optic zone. At opposed sides of the template
fixation means extend from the template body periphery to define
finger and thumb grips 18, 19, respectively. The finger grip has a
narrow neck 21 attached to the template body and connecting a
finger tab 22 to the body. Thumb grip 19 has a narrow neck 24
attached to the body and connecting an arcuate thumb tab 25 to the
body. A central locator index dot 27 in the optic zone, which is a
visual index, enables a user to center the template body on the
cornea in accordance with the observed optic zone of the eye by
means of the fixation tabs 22, 25.
As is best seen in FIG. 3, the template is a semi-spherical shell
with an obverse or outer wall 31 and an inner or reverse wall 32.
The walls differ in curvature and the wall thickness of the
template body therefore varies from the optic zone to the
peripheral template edge 34 outside the limbus circle 15,
diminishing in thickness from the optic zone to the periphery. The
cornea, on the other hand, increases in thickness from the optic
zone to the limbus circle, as is indicated in FIG. 3. In that
Figure the curvature of the cornea outer contour is indicated by
the arc 32 of the template reverse surface. The inner contour of
the cornea is indicated by a broken arc 36, having a radius
centered on the visual axis 35 at a point 37. Displaced along the
visual axis from point 37 is a point 38, from which a radius B
describes the reverse curvature of the template body and the outer
contour of the cornea. Curve line 32 coincides with the epithelium
layer of the eye while curve line 36 coincides with the endothelium
layer within the cornea, which lies between Descemet's membrane and
the liquid of the anterior chamber of the eye. The relationships of
these members of the eye are schematically shown in the partial
sectional view of FIG. 4, wherein the incision in the cornea is
shown being made with a surgical blade 39. Thicknesses are
exaggerated in FIG. 4 for the sake of graphic exposition.
The radii A, B and C are tabulated below for an average cornea:
A=7.6 mm
B=7.5 mm
C=6.29 mm
The displacement of the radial point 38 on the visual axis from
point 37 is 0.66 mm.
One of the important dimensions is the corneal wall thickness,
indicated on the axis by dimension V in FIG. 3, which may be 0.55
mm. At ten degree arcuate intervals from the visual axis are
dimensions W, X and Y. At 50.degree. from the axis is dimension Z.
At each of these dimension points along the corneal vertical arc
the pachometric data must be noted, since the increase in corneal
thickness from optic zone to periphery may not always be
uniform.
As is obvious from FIG. 3, the template thickness at its optic zone
may be about 0.67 mm, but may vary from that dimension with the
type of blade employed. The other dimensions vary from subject to
subject within a definable range.
Again referring to the schematic sectional elevational view of FIG.
4, a template 11 in accordance with the invention is shown in
operative position upon a subject eye 41. Central locator index dot
27 in optic zone 13 is centered over the observed optic zone of the
eye by means of fixation tabs 22, 25(not shown). The position of
locator index dot 27 is normally central of the pupil unless the
pupil and the limbus circle are not concentric, in which case
allowance must be made, based upon the pachometry data, for the
central point of the corneal minimum thickness area. Normally the
dot is aligned with the optical axis of the subject eye.
As can be seen from FIG. 4 surgical knife 39 is inserted in a guide
slit 16 of template 11, preferably adjacent the optic zone, and
plunged into the cornea until the knife point nears the Descemet's
membrane. A shoulder 42 of the knife, from which blade 39A
projects, rests upon the outer surface 31 of the template and the
blade is preferably oriented perpendicular to a tangent to the
template curve at the point of knife entry. The blade is then drawn
across the surface of the template, guided by the slit walls, or
the eye is rotated with respect to the blade, to the termination of
the slit adjacent the limbus of the eye. This procedure is
accomplished while the template is held in place on the eye by the
finger and thumb tabs of the template. Incisions are made
successively in line with each template slit, preferably with
opposite slits of a diametral pair being utilized in turn, until
all of the required incisions are made in the cornea. The template
is then removed and the cornea cleansed and antiseptically treated.
The depth of each incision is then checked and, if necessary, one
or more of the incisions may be deepened.
If the incisions are properly made initially no re-incision is
necessary. It has been found that re-cutting to achieve greater
incision depth increases the danger of perforation of the eyeball
and such perforation can be avoided by initial proper selection of
the template and proper setting of knife blade protrusion from the
knife shoulder or guide, all with due regard to the pachometric and
other data from pre-operative examination.
The pattern of guide slits shown in FIGS. 1 and 2 is known in the
field of this art as "Method A" and is prescribed for correction of
myopia up to 1.00 diopter, with a mean .DELTA.diopter of 0.58.
Obviously not every visual correction can be made with the single
incision pattern made by template 11 of FIG. 1. Typical alternate
patterns are shown in FIGS. 5 through 9, and FIG. 5 shows a guide
slit pattern of a template 43 to correct an astigmatic eye. FIGS.
6, 7 and 8 show templates 44, 45 and 46 with alternate incision
guide patterns for incising corneas of eyes suffering from both
astigmatism and myopia. The prescribed incision pattern and the
consequent guide slit pattern of the template varies with the
degree of myopia and the axis of astigmatism and each FIG. 5
through 8 has legends setting forth the diopter data from which the
pattern derives and the nominal designation of the incision
pattern. Thus, FIG. 6 shows a template 44 with guide slit pattern
of radial lines 16B and chordal lines 47 designated as Method B, in
which the axis of astigmatism is along the axis of the chordal
lines. The eye to be corrected has been shown to have a reading of
from 2.25 to 2.50 diopters, the mean .DELTA.D=1.80.
Similar parameters are noted for FIGS. 7 and 8 for templates 45 and
46.
FIG. 9 shows an alternate embodiment of the invention wherein a
template 50 has a lesser number of radial guide slits than the
template of FIG. 1, but still distributed evenly around the surface
of the template. Measuring rings such as indicia rings 54, 55 in an
optic zone 13A of the template are concentric with indicator dot
27. The rings indicate to the operating surgeon the relationship of
the inner optic zone of the subject eye to the terminations of the
guide slits, terminating inwardly of the template. The eye optic
zone is known from the pachometric data and the rings are of known
diameters and standard for all of the templates upon which they
appear.
Template 50 has alternate fixation means. Small integral suction
cups 51, 52 at diametrically opposed zones on template periphery 53
afford means for fixing the template to the epithelium of the
subject eye. Cup 51 is shown to an enlarged scale in the sectional
elevational view of FIG. 10, wherein the cup is seen to be shallow
and the optic zone 13A is seen to be indented to receive pigment to
define indicator dot 27 and the concentric measuring rings 54, 55
which indicate average corneal optic zones.
Both the apparatus and the process of the invention lend themselves
to to simple eye surgery with major corrective benefits. While some
of the template guide slit patterns for corrective surgery for
specific abberations of vision have been discussed, the apparatus
and the method disclosed lend themselves to a multiplicity of
corrective surgeries that are not defined in this disclosure. The
apparatus is inexpensive to fabricate by techniques and of
materials presently known, and both the apparatus and the method
may be gainfully used by competent surgeons to correct visual
defects within the premises of a well equipped clinic or surgeon's
office with a preciseness, safety and quickness not heretofore
possible.
While the several embodiments illustrated herein encompass many of
the correctable visual defects, the disclosure does not exhaust the
measure of corrections possible when employing the invention. It is
therefore desired that the invention be measured by the appended
claims rather than by the foregoing illustrative specification and
drawing.
* * * * *